Sealing arrangement in hydraulic press

ABSTRACT

A hydraulic press including a cylinder barrel, a piston and a seal housing. The cylinder barrel has an inner peripheral surface. The piston has a pressure side surface and is inserted in the cylinder barrel to form a chamber between the pressure side surface of the piston and the inner peripheral surface of the cylinder barrel. The chamber is configured to contain a hydraulic fluid. The seal housing includes an outer peripheral surface and an inner space which has an inner peripheral wall and which is configured to contain the hydraulic fluid. The seal housing is provided on the pressure side surface of the piston such that the outer peripheral surface is in contact with the inner peripheral surface of the cylinder barrel and such that the hydraulic fluid in the inner space presses the seal housing against the inner peripheral surface.

FIELD OF INVENTION

The present invention relates to a hydraulic press, and morespecifically a hydraulic press provided with a preferably rectangularhydraulic cylinder unit. The rectangular hydraulic cylinder is suitablefor pressing rectangular objects. The hydraulic press according to theinvention also comprises a flexible frame consisting of parallel, flatpillars. A frame of this kind is known from our co-pending SwedishPatent Application No. 9602349-4, filed on Jun. 14, 1996. The inventionrelates particularly to an advantageous scaling arrangement, solving theproblem of leakage in rectangular hydraulic cylinders.

STATE OF THE ART

Rectangular cylinder units are known, as such, in various contexts, e.g.for presses and combustion engines.

It is not previously known, however, to utilise rectangular hydrauliccylinders in hydraulic presses comprising a frame constructed frompillar modules. The pillars support the hydraulic cylinder from twoopposite sides.

SUMMARY OF THE INVENTION

The present invention thus provides a press comprising a hydrauliccylinder unit with a cylinder barrel and a piston. The unit has across-section shape adapted to the product to be pressed. According tothe invention, the press comprises a frame having parallel, flatpillars, surrounding the hydraulic cylinder unit on two opposite sides.

A seal housing is arranged on the hydraulically pressurised side of thepiston, in such a manner as to press the seal housing against theinternal surface of the cylinder barrel, to provide adequate sealing.

The invention is specified in detail by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail below, with reference to theaccompanying drawings, in which:

FIG. 1 is a front view of an embodiment of the hydraulic press accordingto the present invention;

FIG. 2 is a side view of the hydraulic press of FIG. 1;

FIG. 3 is a section view according to the line III—III in FIG. 2;

FIG. 4 is a section view according to the line IV—IV in FIG. 1;

FIG. 5 is a section view according to the line V—V in FIG. 1;

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The invention thus relates to a hydraulic press having a hydrauliccylinder unit with a cylinder barrel and a piston, the cross-sections ofwhich are adapted to the product to be pressed in the hydraulic press.The invention will be described with reference to a rectangular shape,as this shape is at present the most useful one. The advantage of havinga rectangular cross-section of the hydraulic cylinder unit for arectangular product, is that the pressing force will be evenlydistributed across the surface to be pressed. Bending torque on thepress tables outside the products are avoided. With e.g. circularhydraulic cylinder units and rectangular products, thick press tablesare required to distribute the pressing force evenly across the product.Other advantages are that an adapted pressure may be used, and that thedimensions and the weight of the hydraulic press may be generallyreduced in a favourable way.

The hydraulic cylinder unit according to the invention is arranged in aframe as will be described in the following. A patent on the frame hasbeen separately applied for in our Swedish Patent Application No.9602349-4. This frame has many advantages regarding manufacture,transport and assembly, etc., as is described in more detail in saidapplication.

With reference to the drawings, a frame suitable for a hydraulic pressis illustrated, together with part of the machinery equipment for thehydraulic press. Pressing dies and other conventional equipment are notshown in the drawings, for increased clarity in illustrating the idea ofthe invention. The frame generally comprises vertical and parallelplates or pillars 2. In the embodiment shown, the number of pillars isfive. In the pillars 2, a number of holes are provided. Through theseholes run threaded rods 14. The number of vertical pillars 2 and thenumber of threaded rods 14 may of course be varied as necessary.

The pillars 2 are held at correct distances from each other by means ofnuts 15, which are placed on both sides of each plate 2, and which aretightened to fix the pillars in position. The distance between thepillars can be easily adjusted by loosening the nuts and screwing themin one direction or the other to displace the pillar located betweenthem. In this manner, the distance between the pillars 2 may be setcompletely arbitrarily.

In order to further stabilise the frame, and to fasten items ofmachinery, a horizontal top plate, here called roof 1, is preferablyattached to the upper side of the frame. The roof 1 may conveniently befastened by screws, as shown in the drawings.

The frame is also preferably equipped with a bottom plate or mounting13, fastened by screws and angle irons 16.

The hydraulic press frame further comprises an upper press table 3 and alower press table 12 for fixing the hydraulic press, the press table 3being provided with entrance holes for the hydraulic and otherconnectors of the hydraulic press. The press tables are fastened to thedifferent plates by their respective screws, see e.g. at 11.

Referring now particularly to FIG. 3, the design of the hydrauliccylinder unit is illustrated. The hydraulic cylinder unit comprises acylinder barrel 4 having an approximately rectangular cross-section (seeFIGS. 4 and 5). The cylinder barrel 4 is fastened to the upper presstable 3 by means of screws. The barrel has a hydraulic pressure inlet 5for hydraulic fluid. The hydraulic fluid acts upon the top side of apiston 8, having a corresponding cross-section. The piston 8 is attachedto a moving press table 10. An object to be pressed is placed betweenthe moving press table 10 and the lower press table 12.

When the hydraulic fluid is pressurised inside the barrel, the latter issubjected to a certain deflection, which is somewhat waved, due to thebarrel only being supported at the pillars 2, see in particular thesection views of FIGS. 4 and 5. The piston 8, however, is only subjectedto an axial pressure and does not deflect sideways. If the piston 8 hadbeen equipped with conventional seals between the piston 8 and thecylinder barrel 4, a wave-shaped clearance would have been created here,which had been difficult to seal off.

The present invention, however, includes a new sealing arrangementallowing an efficient seal between piston and barrel. A seal housing 6is provided on the pressure side of the piston 8. As is best seen inFIGS. 4 and 5, the seal housing is shaped like a rectangular ring.Consequently, the hydraulic pressure acts on the inside of the sealhousing, pressing it against the inner surface of the barrel 4. The sealhousing 6 is made of a relatively flexible or soft material, so as to beable to adapt to the deflection of the barrel. A preferred material isbronze, but other materials are also conceivable, e.g. plastics.

The seal housing is fixed to the piston by fastening means extending,with a clearance (not visible), in holes in the seal housing. Theclearances are large enough for the seal housing to be able to followthe deflection of the cylinder barrel 4 without causing any stressing ofthe piston 8.

In order to further improve the seal, hydraulic seals 7A, 7B areprovided in grooves in the seal housing 6. Preferably, there is alateral seal 7A between the seal housing 6 and the barrel 4, as can beseen in the section view of FIG. 4, and an axial sealing device 7Bbetween the seal housing 6 and the piston 8, as can be seen in thesection view of FIG. 5. The sealing devices are compressed to so calledzero play for an efficient sealing function.

The present invention thus provides a hydraulic press having the abovedescribed advantages.

As has been mentioned above, and as is evident for a person skilled inthe art, many modifications and variations are conceivable, withoutdeviating from the scope of the invention as defined by the followingclaims.

What is claimed is:
 1. A hydraulic press comprising a hydraulic cylinderunit, having a cylinder barrel, a piston, and a seal housing, and beingarranged to contain a hydraulic fluid in a volume enclosed by saidcylinder barrel and said piston, defining a pressure side on one side ofsaid piston, wherein said seal housing is mounted on the pressure sideof the piston in contact with an inner surface of said cylinder barreland is movable relative to the piston, and provided with an inner spacehaving an internal wall, said inner space being arranged to contain apart of the hydraulic fluid, in such a manner that the hydraulic fluidacts on said internal wall, whereby the hydraulic pressure forces theseal housing against the inner surface of the cylinder barrel to followthe inner surface of the cylinder barrel.
 2. A hydraulic press accordingto claim 1, wherein the seal housing is attached to the piston in aradially displaceable manner.
 3. A hydraulic press according to claim 2,wherein the seal housing is attached to the piston by means of fasteningmeans extending, with a clearance, through holes in the seal housing. 4.A hydraulic press according to any one of claims 1, 2, or 3, wherein theseal housing is made of a flexible material.
 5. A hydraulic pressaccording to claim 4, wherein the seal housing is made of bronze.
 6. Ahydraulic press according to claim 4, wherein the seal housing is madeof plastics.
 7. A hydraulic press according to claim 1, wherein at leastone sealing device is provided in a groove in the seal housing.
 8. Ahydraulic press according to claim 7, wherein one of said at least onescaling device is arranged in a lateral groove and in contact with theinner surface of the cylinder barrel, and wherein another of said atleast one sealing device is arranged in an axial groove and in contactwith the surface of the piston.
 9. A hydraulic press according to claim7, wherein the sealing device is compressed to zero clearance.
 10. Ahydraulic press according to claim 1, wherein the cross-section shape ofthe cylinder unit is rectangular.
 11. A hydraulic press comprising: acylinder barrel having an inner peripheral surface; a piston having apressure side surface and inserted in the cylinder barrel to form achamber between the pressure side surface of the piston and the innerperipheral surface of the cylinder barrel, the chamber being configuredto contain a hydraulic fluid; and a seal housing including an outerperipheral surface and an inner space which has an inner peripheral walland which is configured to contain part of the hydraulic fluid, the sealhousing being provided on and being movable relative to the pressureside surface of the piston such that the outer peripheral surface of theseal housing is in contact with the inner peripheral surface of thecylinder barrel and such that the hydraulic fluid in the inner spacepresses the seal housing against the inner peripheral surface acting onthe inner wall of the seal housing to follow the inner peripheralsurface of the cylinder barrel.
 12. A hydraulic press comprising ahydraulic cylinder unit, having a cylinder barrel, a piston, and a sealhousing, and being arranged to contain a hydraulic fluid in a volumeenclosed by said cylinder barrel and said piston, defining a pressureside on one side of said piston, wherein said seal housing is made of aflexible material and is mounted on the pressure side of the piston incontact with an inner surface of said cylinder barrel, and provided withan inner space having an internal wall, said inner space being arrangedto contain a part of the hydraulic fluid, in such a manner that thehydraulic fluid acts on said internal wall, whereby the hydraulicpressure forces the seal housing against the inner surface of thecylinder barrel to follow the inner surface of the cylinder barrel. 13.A hydraulic press comprising: a cylinder barrel having an innerperipheral surface; a piston having a pressure side surface and insertedin the cylinder barrel to form a chamber between the pressure sidesurface of the piston and the inner peripheral surface of the cylinderbarrel, the chamber being configured to contain a hydraulic fluid; and aseal housing made of a flexible material and including an outerperipheral surface and an inner space which has an inner peripheral walland which is configured to contain the hydraulic fluid, the seal housingbeing provided on the pressure side surface of the piston such that theouter peripheral surface of the seal housing is in contact with theinner peripheral surface of the cylinder barrel and such that thehydraulic fluid in the inner space presses the seal housing against theinner peripheral surface acting on the inner wall of the seal housing tofollow the inner peripheral surface of the cylinder barrel.